<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"> 
<title>CSS基本语法</title> 
<style>
.marked p{
    color:lawngreen
}
</style>
</head>

<body>
    <p>这是在marked类外面</p>
    <div class="marked">
        <p>这是在marked类内部</p>
    </div>
</body>
</html>